Well, it used to be possible before Android 11, that's the thing.
So, following a bit the example I was giving, if you want to sync data from another app to backup it (or whatever), and that App stores its data in the default data folder assigned by Android, since Android 11 it's going to be very difficult to do it.
I used to sync some of those folders with Syncthing in Android, and since Android 11 things have gotten complicated (meaning, you need 'all files' access, and even then, some things might not be accessible). [0]
Hello, we and TFA are talking about the new API where the user picks what directory an app has access to vs. the old API where the app has access to almost everything as you pointed out.
The Google Play store (not Android the OS) is now limiting access to the old API, it has nothing to do with Android 11.
The new API does not work with Linux open(). Some projects (like Syncthing) don't want to put in the work to switch to the new API.
Yeah, I'm not saying that you're in the wrong, I'm saying that they might want to access further than the new `ACTION_OPEN_DOCUMENT_TREE` API call allows. For example, the Downloads folder (you can only open individual files with ACTION_OPEN_DOCUMENT, not the whole folder). And that can be reached with the `MANAGE_EXTERNAL_STORAGE` (all files) API. Is that OK? Well, it's not intrinsically bad, but it clashes with Google's Android hardening directives.
Not very familiar with the NextCloud client, as I haven't used it much, but in the case of Syncthing (and this is totally guessing from what I remember from reading the forums back when the Android 11 upgrade happened): I don't think they don't want to put the work to switch to the new API, I think they want to access places they won't be able to access with the new API, so that's why they won't change the calls.
So, following a bit the example I was giving, if you want to sync data from another app to backup it (or whatever), and that App stores its data in the default data folder assigned by Android, since Android 11 it's going to be very difficult to do it.
I used to sync some of those folders with Syncthing in Android, and since Android 11 things have gotten complicated (meaning, you need 'all files' access, and even then, some things might not be accessible). [0]